?6.5 mm 55SiCr淬回火弹簧钢丝滞后断裂研究

Research of diameter 6.5 mm 55SiCr quenched and tempered spring steel wire delayed fracture

Ф6.5mm55SiCr淬回火弹簧钢丝热处理后探伤涂油前发生滞后断裂。对钢丝断裂样品化学成分、力学性能、断口形貌、晶粒度、表面质量和显微组织进行研究。钢丝断裂样品化学成分、力学性能满足标准要求,断口宏观形貌起伏较大,钢丝实际晶粒度为7.7级,淬回火弹簧钢丝显微组织为回火屈氏体加极少量小球状碳化物。结果表明,Ф6.5mm55SiCr淬回火弹簧钢丝滞后断裂主要是由于钢丝次表层存在较大尺寸非金属夹杂物引起的氢致滞后断裂。

Diameter 6.5 mm 55SiCr quenched and tempered spring steel wire occurred delayed fracture after heat treatment and before flaw detection oil coating.To research the chemical composition,mechanical properties,fracture pattern,grain size,surface quality and microslructure of steel wire fracture samples.The chemical composition,mechanical properties meet requirements of standard,fracture macro pattern fluctuate obviously,steel wire actual grain size grade is 7.7,microstructure of quenched and tempered spring steel wire is tempered troostite with very small amount of spheroidal carbide.Results show that diameter 6.5 mm 55SiCr quenched and tempered spring steel wire delayed fracture is hydrogen-induced delayed fracture mainly caused by large non-metallic inclusion in subsurface layer of steel wire.